More than two dozen said they were concerned about decision-making at the agency.
The FDA's chief spokesperson has been fired after President Donald Trump and FDA Commissioner Dr. Stephen Hahn were widely criticized for exaggerating the benefits of blood plasma treatment for COVID-19.
Experts questioned claims by the administration that the treatment reduces mortality by 35 percent in some COVID-19 patients.
U.S. President Donald Trump suggested that the "deep state" at the FDA deliberately delayed developing a COVID-19 vaccine.
Dr. Stephen Hahn repeatedly declined responses to President Trump's claim that 99 percent of coronavirus cases are "totally harmless."
Stephen Hahn said coronavirus testing will be necessary beyond May and "into the fall," as he acknowledged the U.S. is "very close to the peak" of active cases.
FDA Commissioner Hahn said the new policies would help address "urgent public health concerns by helping to expand the number and variety of diagnostic tests, as well as available testing capabilities in health care settings, and reference and commercial laboratories."